Diazotype reproduction material



United States Patent 3,360,369 DIAZOTYPE REPRODUCTION MATERIAL Luigi Amariti, Chicago, Peter Panlon, Jr., Berwyn, Carl Jones Marshall, Melrose Park, and Gerson E. Beauchamp, Chicago, Ill., assignors to Eugene Dietzgen Co., Chicago, 11]., a corporation of Delaware No Drawing. Filed May 1, 1964, Ser. No. 364,271 12 Claims. (Cl. 96-75) The present invention relates to diazotype reproduction materials and to methods of forming graphic reproductions utilizing said materials.

In a diazotype process a carrier or support, such as a sheet of paper, plastic, or the like, is provided with a light-sensitive layer or coating which includes a stabilized light-sensitive diazo compound. When the lightsensitive layer is made sufficiently alkaline, the diazo compound will react with an azo dye coupler to form an intensely colored azoic dye. The coupler is either included in the light-sensitive layer or the light-sensitive layer is treated with the coupler during a subsequent step in the process.

There are three principal diazotype reproduction processes. In all three processes an image ordinarily is produced by exposing the sensitized layer to actinic light transmitted through the original which is to be copied. The areas of the original bearing the material to be copied inhibit the passage of light (usually ultraviolet light having a wave length of from 3400 A. to 4100 A.) and, consequently, the diazo compound in these areas is retained. In the other areas the light reaches the sensitized layer and destroys the diazo compound. Upon completion of this printing step the base containing the diazo compound has been formed into a precise duplication of the original, the duplicate being pale yellow in color (the color of the diazo).

When the exposure has been completed, the image is developed by rendering the light-sensitive layer or coating alkaline. It is in this step that the three principal processes difier. In the most widely used development process the formation of the azoic dye is accomplished by contacting the light-sensitive layer with moist ammonia gas. The coating composition contains both the diazo as the light-sensitive member and the coupler which is an essentially colorless compound capable of reacting under appropriate conditions with the diazo compound to form the highly colored azoic dye. An atmosphere of warm, moist ammonia causes the diazo component and coupler to react. The function of the ammonia is to raise the pH level of the sensitive layer.

If the diazo paper is to be stored for reasonably long periods of time before it is used, the diazo and coupler components must be kept under conditions so as to prevent precoupling. Precoupling is prevented by adding certain acids to the light-sensitive layer. These acids can include organic acids such as citric, tartaric, etc., or inorganic acids such as sulfuric acid, perchloric acid, etc. Other additives that are included'in the light-sensitive layer to prevent precoupling include acidic salts such as zinc chloride, magnesium chloride, cadmium chloride, etc. The combination of acids and metallic salts tends to create in the paper a reasonably high acidity level. This acidity must be neutralized by the warm, moist ammonia gas during the development stage so as to allow a basic condition to exist. As was pointed out above, such a basic condition is required if the diazo and coupling components are to combine.

Modern ammonia developing equipment for diazo systems operates at very high rates of speed, as high as 150 feet per minute. Under these conditions the length of time of contact of the light-sensitive coating or layer with 3,360,369 Patented Dec. 26, 1967 the ammonia vapors is of extremely short duration. For this reason it is essential to increase the rate of neutralization of the acidic stabilizing materials during the development cycle. In the past, materials such as glycerine, ethylene glycol, and other hygroscopic materials have been employed for this purpose. These compounds accelerate the rate of neutralization by drawing moisture into the coating during the development cycle. Inasmuch as ammonia has a high afl'inity for moisture, it also is drawn into the coating. The humectants or hygroscopic materials also serve as a reaction medium in which develop ment can occur. If no hygroscopic materials or humectants were included in the light-sensitive stratum or layer, one would have a coating consisting essentially of solid materials. It would then be necessary to cause a relatively ditlicult solid-to-solid reaction to occur in the paper. The liquid humectants or hygroscopic materials both in themselves and with the water which is drawn into the layer by the humectants serve as a reaction medium.

The use of hygroscopic materials in ammonia developed systems has not provided an entirely satisfactory process at high development speeds. If too great an amount of the hygroscopic material is used, the resultant coating will have poor storage properties and a very undesirable greasy, limp feel. For these reasons, the acceleration of development by known means is subject to serious limitations.

It is an object of the present invention, therefore, to provide a superior diazotype formulation which can be used with ammonia gas developing systems.

Another object of the invention is to provide a diazotype formulation having improved feel and shelf life characteristics.

Still another object of the invention is to provide a diazotype formulation which can be used with ammonia gas developing systems, which formulation does not require the use of substantial amounts of hygroscopic materials.

Still another object of the invention is to provide a diazotype formulation which can be neutralized very rapidly when contacted with ammonia gas.

The second principal diazotype reproduction process is one in which the diazo-bearing support is immersed in an alkaline or acidic solution of a coupling component. The coupling component is selected so that coupling can occur under either acidic or alkaline conditions. In this so-called liquid development system it is important that the development take place across the entire coated surface of the paper or other support. It often happens, however, that the support is incompletely coated with the diazo formulation. When the support is immersed in the alkaline or acidic solution of coupling component areas of the original are not developed. This problem is usually referred to as skipping. When this occurs important information that is contained on the original may not be transferred to the copy.

It is another object of the present invention to provide a diazotype formulation which can be used in connection with liquid developing systems which substantially eliminates the problem of skipping.

' The third principal diazotype system is referred to as a 1 heat developable system. This system differs from the first system described above in that the development of the azoic dye is effected by applying heat to the lightsensitive layer or stratum. The light-sensitive layer or stratum includes a diazonium compound, a coupler, and acidic stabilizing materials. In addition, the light-sensitive layer or stratum includes a material which produces an alkaline reaction when heated. The heat causes the generation of an alkaline substance which, in turn, neutralizes the acidic stabilizing materials and creates a condition whereby the diazonium compound and the coupler can unite. Heat developable systems of the type referred to in the subject specification include those described in U.S. patent application Ser. No. 5,688 filed February 1, 1960, and US. patent application Ser. No. 279,331 filed May 9, 1963, now Patent No. 3,316,092. The disclosure of these applications is incorporated in the subject application by reference.

The material most commonly used to produce an al kaline reaction when heated is urea. When urea is decomposed by heat, ammonia is generated which neutralizes the acidic materials present in the light-sensitive layer and effects development. In addition to urea, guanidine, alkyl-substituted ureas and alkyl-substituted guanidines have been used to effect coupling through the formation of ammonia.

Urea and like compounds have a number of disadvantages when employed in heat developable systems. These disadvantages include the following:

(1) The temperature necessary to effect development is relatively high and, consequently, undue amounts of heat are generated during the development cycle. This high temperature in turn has a tendency to scorch the paper as well as to create discomfort to persons in the areas immediately surrounding the machine.

(2) Due to the quantity of urea required in this type of formulation, excessive amounts of chemical deposits are formed in the apparatus that is used to develop the reproduction. These deposits tend to accumulate and impair the mechanical functioning of the developing apparatus.

It is, therefore, another object of the subject invention to provide a diazo formulation which can be used in a heat developable system which overcomes the problems described above. In particular, it is an object of the invention to provide a heat developable system which lowers the temperature necessary to effect development and which prevents the formation of large amounts of chemi' cal deposits in the developing apparatus.

In general, the first embodiment of the subject invention is based on the discovery that the incorporation of dimethyl sulfoxide in a diazotype formulation that is to be developed by moist ammonia gas greatly increases the rate of neutralization of the acidic materials in the formulation. A further discovery of great importance was the fact that the use of dimethyl sulfoxide provided shelf life characteristics which were much superior to those obtained using conventional hygroscopic materials or bu rnectants. The use of dimethyl sulfoxide in a system that is developed with ammonia gas makes it possible to form an extremely stable light-sensitive coating which is capable of rapid neutralization whereby development can occur at a high rate of speed.

The second embodiment of the invention is based on the discovery that the incorporation of dimethyl sulfoxide in a diazo formulation which is to be used in a liquid or moist system along with powdered or granulated starch such as wheat starch tends to prevent skipping from taking place.

The third embodiment of the invention is based on the discovery that the addition of dimethyl sulfoxide to a heat developable diazotype formulation substantially improves the performance of that formulation. In this system, dimethyl sulfoxide catalyzes the chemical reactions and consequently expands the number of base generators that can be employed in the process. The use of dimethyl sulfoxide also lowers the temperature at which urea will decompose. While the mechanism of the reaction is not fully understood, it is believed that the dimethyl sulfoxide serves to accelerate the decomposition of the base generating material via the mechanism of hydrolysis when mildly acidic materials such as conventional stabilizers are present. The base generating material such as an amide or nitrile decomposes through hydrolysis. The dimethyl sulfoxide serves as a reaction medium in which hydrolysis of the potential ammonia producer can occur with great speed.

The following examples are illustrative of the subject invention.

EXAMPLE 1 The three formulations set forth below were used in an ammonia developed system.

Black Line Formulation 4-diazo 2,5 diethoxyphenylmorpholine zinic chloride salt g 23 High Speed Blue Line Formulation Water l 1 Dimethyl sulfoxide cc 150 Citric acid g 20 H2504 CC-.. 3 Caffeine or allylthiourea g 30 Amide of fi-oxynaphthoic acid and a-morpholino propylamine g 25 ZnCl g.. 40 4-diazo-2,5-diethoxyphenylmorpholine zinc chloride salt g 13 Sepia Intermediate Water 1 1 Dimethyl sulfoxide cc Citric acid g 70 ZnCl g 50 Thiourea g 50 Resorcinol ..g 20 -p-Diazo-N,N-dimethylaniline zinc chloride salt g 50 In each case semitransparent diazo process paper was coated with the designated formulation at a rate of about 1 liter of sensitizing solution per 900 sq. ft. of paper. The coating rate, of course, can vary widely. In general, however, the application of the sensitizing solution to the paper is made at a rate of about 10 to 50 grams of diazo compound per 1,000 sq. ft. of paper. With respect to paper coated with each formulation, the paper was air dried and was then placed in sandwich relationship with a superimposed original containing typed characters. The sandwich was exposed to ultraviolet radiation to destroy the diazo in all areas except those portions screened by the typed characters and then was passed through an ammonia gas developing unit. Excellent reproductions were produced in each instance. The coated paper also had excellent shelf life characteristics as well as satisfactory feel.

EXAMPLE 2 This example illustrates the use of the subject inven tion with respect to a moist developed formulation. In preparing the paper, a starch which closely resembles rice starch in its physical characteristics, was soaked overnight with dimethyl sulfoxide. It was found that a finely dispersed starch emulsion was obtained by adding water to the mixture. The emulsion, when formulated with suitable binders such as polyvinyl acetate and additive quantities of silica, produced a base which could be coated with a sensitizer solution in such a manner that the resultant product had substantially no tendency to cause skipping. The sensitizers that can be used with this embodiment of the invention are those which commonly are employed in moist development systems. About 50 grams of starch are used per cc. of dimethyl sulfoxide 7 in coating the paper. This amount can vary from about 10 to 60 grams, and preferably from about 25 to 50 grams of starch per 100 cc. of dimethyl sulfoxide.

EXAMPLE 3 This example illustrates the use of the subject invention with respect to thermally developed formulations. The following formulations were coated on semitransparent diazo process paper at a rate of approximately 1 liter of sensitizing solution per 900 sq. ft. of paper.

Thermally Developed Formulations Water l 1 Guanidine carbonate g i 50 H2804 CC Dimethyl sulfoxide cc O CdSO g 100 Urea g 300 D-Salt g 40 Thiourea g p-diazo l-morpholinobenzene 4-diazonium chloride g 20 Starch g 50 Syloid 244 g 5 Water l 1 Dimethyl sulfoxide ml 150 Biuret g 100 Cyanoguanidine -g 80 D-Salt g 80 Boric acid g 5 m-Benzenedisulfonic acid g 100 Polyvinyl acetate Emulsion S98 cc 50 Syloid 244 g 50 1-morpholinobenzene-4-diazonium chloride g '20 Saponin g 2.5

* Shawinigan and Cabot, respectively.

2 2,3-dihydroxynaphthalene-G-sodium sulfonate.

After the paper had been air dried it was placed in sandwich relationship with a superimposed original containing typed characters. The sandwich was exposed to ultraviolet radiation to destroy the diazo in all areas except those portions screened by the typed characters. The paper was then heated to a temperature of about 300 F. in a developing machine of the type described in US. Patent 3,012,141. The reproduction was of high quality and had excellent shelf life characteristics.

A wide variety of diazo compounds can be used in the subject formulations. The nature of the particular diazo compound does not constitute a part of the subject invention. It is preferred to employ as the diazo compound one of the commonly used stabilized diazonium salts, preferably the zinc chloride double salt. Other stabilized derivatives may be used, for example, the cadmium chloride or stannic chloride double salts, or the fluoborates.

Exemplary diazo compounds which may be employed are the diazonium salt-s obtained by diazotization of the following amines:

p-amino-N,N-dimethylaniline p-amino-N,N-diethylaniline p-amino-N,N-dipropylaniline p-amino-N-ethyl-N-propylaniline p-amino-N-ethylaniliue p-amino-N-ethyl-N-B-hydroxyethylaniline p-amino-N-methyl-N-B-hydroxyethylaniline p-amino-N,N-di-B-hydroxyethylaniline p-amino-methoxy-N,N-diethylaniline p-arnino-N-ethyl-o-toluidine p-amino-N-ethyl-m-toluidine p-amino-N,N-diethyl-m-toluidine p-amino-N-ethyl-N-hydroxyethyl m-toluidine p-amino-N-ethyLN-benzylaniline p-amino-N-ethyl-N- S-hydroxyethyl-m-toluidine N-p-amino-phenylmorpholine 6 N- (2,5-diethoxy-4-aminophenyl)-morpholi.ue p-amino-diphenylamine 3-aminocarbazole and the like.

alkyl, or a radical which together with R and N forms a radical of a cyclic basic amine. R and R may be hydrogen, alkyl, or alkoxy. The several alkyl radicals are preferably lower alkyl radicals. In addition to these preferred compounds, it is contemplated that other compounds might be employed, such as those having the foregoing composition and which contain an acyl group as R, and/or R .The following azo coupling agents are among those which can be used in the subject process and in preparing subject products:

2,3-dihyd-roxynaphthalene 2,3-dihydroxynaphthalene-6-sul-fonic acid Resorcinol Acetoacetanilide 7-hydroxy-1,2-naphthimidazole l-phenyl-3-methyl-5-pyrazolone 2-naphthol-3,6-disulfonic acid and the like.

When employing the coupling components having a high coupling energy, such as resorcinol and acetoacetanilide, it is advisable to select a diazo compound having a small coupling energy, and the diazo layer may require a higher degree of stabilization against precoupling.

' In the first and third embodiments of the invention it is important to add an acid stabilizing agent to the composition. These agents include inorganic acids such as sulfuric acid, perchloric acid, etc., and organic acids such as malonic, gluconic, cyanoacetic, maleic, tartaric, citric, diglycolic, oxalic, acetic, and malic acids, and anhydrides of such acids, e.g., the lactones. Reference to such acids is intended to include the equivalent anhydrides.

' The preferred compounds which produce an alkaline reaction when heated and which are used in the third embodiment of the invention include those which yield ammonia by decomposition or dissociation. The compounds include, for example, the ureas, i.e., urea and itS derivatives, in particular, guanidine, alkyl substituted urea and alkyl substituted guanidines, said alkyl groups con taining from 1 to 4 carbon atoms such as .methyl urea, ethyl urea, propyl urea, and butyl urea, and hydroxy ureas such as hydroxy methyl urea and hydroxy ethyl urea. It is often advantageous to use a plurality of such compounds, such as mixtures of urea and guanidine, and urea and tetramethyl guanidine. Other compounds of this type which can be used in the subject process include sulfamide and cyanamide.

With respect to the amount of dimethyl sulfoxide that is used in the formulations, it will be clear to one skilled in the art that the quantity will differ from prod net to product. In formulations that are developed with ammonia gas where it is desired to obtain blue or black line copies, the wide range of dimethyl sulfoxide will be from about 1 to 30% by volume based on the water in the formulation. The preferred range would 'be from about 5 to 20%, and the most preferred range from about 8 to 17%. This amount of dimethyl sulfoxide is about equal to from 10 to 350 ml. of dimethyl sulfoxide per 900 sq. ft. of paper or other base material. The preferred range is from 50 to 250 ml. per 900 sq. ft. of paper, and the most preferred is from 100 to 200 ml. of dimethyl sulfoxide per 900 sq. ft. of paper. In ammonia developed formulations that are suitable for the production of sepia intermediates the broad range is from about 1 to 25% dimethyl sulfoxide based on the water in the formulation, the preferred range is from 3 to 10%, and the most preferred range is from 5 to 8%. The broad range of dimethyl sulfoxide would be from about 10 to 275 ml. per 900 sq. ft. of paper. The preferred range would be from about 30 to 125 ml. of dimethyl sulfoxide per 900 sq. ft. of paper or other base material, and the most preferred range would be from about 50 to 100 ml. of dimethyl sulfoxide per 900 sq. ft. of paper. With respect to the use of the subject invention in a heat developable system, the broad range is from about 1 to 30% dimethyl sulfoxide based on the water in the formulation, and the preferred range is from about 5 to The broad range of dimethyl sulfoxide would be about 10 to 350 ml. per 900 sq. ft. of paper or other base material, while the preferred range would be from about 50 to 175 ml. per 900 sq. ft. of paper, and the most preferred range would be from about 80 to 150 ml. of dimethyl sulfoxide per 900 sq. ft. of paper. These quantities, of course, will vary in accordance with the particular system that is being employed.

In general, one liter of sensitizing solution will coat approximately 100 sq. yds. of paper or 900 sq. ft. of paper. The formulations that are set forth in the examples are generally made up with one liter of water. When the chemicals are dissolved in the water the volume is brought up to about 1200 to 1300 milliliters.

In the ammonia developable system, the essential components of the sensitizing solution include a diazo compound, a coupler, acidic stabilizers, and dimethyl sulfoxide. In the thermally developed system, the essential components include the diazo compound, the coupler, an acidic stabilizer or stabilizers, dimethyl sulfoxide, and a material capable of generating alkali under the influence of heat. As has been pointed out previously, the dimethyl sulfoxide catalyzes the decomposition of the base-generating material so that the decomposition occurs more rapidly and at lower temperatures than in conventional systems.

The preferred base generators that can be used in conjunction with dimethyl sulfoxide in the third embodiment of the invention include cyanoguanidine, biuret, and guanidine sulfate. Guanidine sulfate is formed from the reaction of guanidine carbonate on sulfuric acid. Urea is also a preferred base generator in the system containing dimethyl sulfoxide. In the present system, urea is capable of being decomposed at a lower temperature than ordinarily is required.

Organic nitrogen base salts which produce an alkaline reaction when heated may be employed, particularly salts of amines with volatile or decomposable acids such as acetic acid, malonic acid, g-luconic acid, and other heat fugitive acids. A mino-panaflins and especially hydroxylated derivatives thereof or amino alcohols are preferred, particularly those having low volatility, substantial alkalinity, and no odor, and which are resistant to oxidation. Examples of such amines are tri-(hydroxymethyl)-aminomethane, 2-amino-2-methyl-1, 3-propanediol, ethanolamine, diethanolamine, and ethyl diethanolamine. These materials are used in conjunction with appropriate acid stabilizers. The aforementioned guanidines are also basic, and their basicity may provide or contribute to the necessary alkaline reaction, with or without decomposition thereof to produce ammonia. Other compounds which are contemplated include the ammonium salts of weak acids, such as ammonium gluconate, ammonium acetate, ammonium carbonate, ammonium diglycolate, and ammo-' nium oleate. The compounds containing the ammonium ion presently are not preferred as the materials produced therewith tend to have a reduced shelf life.

In the third embodiment of the invention, the thermally developable paper usually receives approximately a 370 wrap and is passed under a heat source at speeds of approximately 14 feet per minute. The temperature range employed in such processes generally is approximately 280 to 320 F. These aspects of the process, of course, do not constitute a part of the subject invention.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. Reproduction material which comprises: a supported layer of an ultraviolet light-sensitive material, said material including a coupling diazo compound and dimethyl sulfoxide.

2. Reproduction material which comprises: a supported layer of an ultraviolet light-sensitive material, said material including a coupling diazo compound, an azo coupling component, and dimethyl sulfoxide.

3. Reproduction material which comprises: a supported layer of a light-sensitive heat developable composition, said composition including a mixture of a coupling diazo compound, an azo coupling component, a compound producing an alkaline reaction when heated, said compound being present in an amount sufficient to effect coupling of said diazo compound and said coupling component when heated, and dimethyl sulfoxide.

4. Reproduction material which comprises: a paper base, an ultra-violet light-sensitive layer supported on said paper base, said ultraviolet light-sensitive layer including a coupling diazo compound and dimethyl sulfoxide, the amount of dimethyl sulfoxide included in said layer being from about 10 to about 350 ml. per 900 sq. ft. of said paper base.

5. Reproduction material which comprises: a paper base, a supported layer of an ultraviolet light-sensitive material, said material including a coupling diazo compound, an azo coupling component, and dimethyl sulfoxide, the amount of dimethyl sulfoxide being present in an amount from about 10 to 350 ml. per 900 sq. ft. of said paper base.

6. Reproduction material which comprises: a paper base, a supported layer of a light-sensitive heat developable composition, said composition including a mixture of a coupling diazo compound, an azo coupling component, a compound producing an alkaline reaction when heated, said compound being present in an amount sufficrent to effect coupling of said diazo compound and said coupling component when heated, and dimethyl sulfoxide, the amount of dimethyl sulfoxide being present man amount from about 10 to 350 ml. per 900 sq. ft. of said paper base.

7. Reproduction material which comprises: a paper base, a supported layer of a light-sensitive heat developable composition, said composition including a mixture of a coupling diazo compound, an azo coupling component, a compound producing an alkaline reaction when heated, said compound being present in an amount sufficient to effect coupling of said diazo compound and said coupling component when heated, and dimethyl sulfoxide, the amount of dimethyl sulfoxide being present in an amount from about 50 to ml. per 900 sq. ft. of said paper base.

8. Reproduction material which comprises: a paper base, a supported layer of a light-sensitive heat developable composition, said composition including a mixture of a coupling diazo compound, an azo coupling component, a compound producing an alkaline reaction when heated, said compound being present in an amount sufficient to effect coupling of said diazo compound and said coupling component when heated, and dimethyl sulfoxide, the amount of dimethyl sulfoxide being present in an amount from about 80 to 150 ml. per 900 sq. ft. of said paper base.

9. Reproduction material which comprises: a paper base, a supported layer of an actinic light-sensitive material, said material including a coupling diazo compound, an azo coupling component, and dimethyl sulfoxide, the amount of dimethyl sulfoxide being present in an amount from about 50 to 250 ml. per 900 sq. ft. of said paper base.

10. Reproduction material which comprises: a paper base, a supported layer of an ultraviolet light-sensitive material, said material including a coupling diazo compound, an azo coupling component, and dimethyl sulfoxide, the amount of dimethyl sulfoxide being present in an amount from about 100 to 200 ml. per 900 sq. ft. of said paper base.

11. Reproduction material which comprises: a paper base, a first layer on said paper base, said first layer consisting essentially of an emulsion of starch particles and dimethyl sulfoxide, the amount of starch in said emulsion varying from about 10 to 60 grams per 100 cc. of dimethyl sulfoxide, the amount of dimethyl sulfoxide in said layer being from about 10 to 275 ml. per 900 sq. ft. of paper; and a second layer supported on said base, said second layer including a light-sensitive coupling diazo compound.

12. Reproduction material as in claim 6 wherein said compound producing an alkaline reaction when heated is selected from the group consisting of urea, cyanoguanidine, biuret, and guanidine sulfate.

References Cited UNITED STATES PATENTS OTHER REFERENCES Technical Information on Dimethylsulfoxide, Crown Zellerbach Corporation, August 1959, Comas, Washington (page 1 relied on).

T. L. Fletcher et al.: Chemistry and Industry, January-March 1961, London, England (pages 179-180 relied on).

NORMAN G. TORCHIN, Primary Examiner.

C. L. BOWERS, Assistant Examiner. 

1. REPRODUCTION MATERIAL WHICH COMPRSES: A SUPPORTED LAYER OF AN ULTRAVIOLET LIGHT-SENSITIVE MATERIAL, SAID MATERIAL INCLUDING A COUPLING DIAZO COMPOUND AND DIMETHYL SULFOXIDE. 